PWM driver tested in RTEMS with RGB

punit vara punitvara at
Fri May 27 19:53:54 UTC 2016

On Thu, May 12, 2016 at 6:55 PM, Martin Galvan
<martin.galvan at> wrote:
> Hi Punit! Sorry I didn't answer, I was off sick for a couple days. Marcos
> and I are a bit crowded so we can't review every bit of your patch right now
> (plus we don't have our BBB anymore). Could you make the RGB test work using
> SW code only?
Hi all,

I tested test suite which only use TI SW API. Like as follow :

Whatever frequency  I change LED glows continuously only. In between
CMPA or CMPB whichever is higher , that respective EPWMA or EPWMB is
more brighter.That is the only difference I found out.

Second test case which is with custom function not with TI SW only :

Here whatever frequency I pass as argument , LED blinks at same rate.
There is no difference. If I set different duty cycle for EPWMA and
EPWMB, LED glowing time is more for which duty cycle is higher. But it
seems in this case PWM wave generates , not sure at which frequency.

To calculate frequency(UP or DOWN count only) equation is


In program we need to assign value to TBPRD register.

Another important equation to remember is


How to calculate duty cycle ?

Simply value need to pass to CMPA or CMPB register.

I am trying to generate testcase which can generate different
frequencies with different duty cycle on LED with TI SW. I tried to
debug with printf but dont know how to use that results. Can you
suggest me any test cases so that I can able to find what is the
problem with code ? Any conclusion why in one case LED just blinks and
in another it just glows continuous. ?

Any help will be appreciated. :-)

Thank you,
Punit Vara

More information about the devel mailing list